1. Filed of the Invention
The present invention relates to an improvement of a one-to-one line switching system having a transmitting part and a receiving part, each part having one-to-one line switching equipment for switching between hot lines and standby lines in a one-to-one correspondence, and a switch control part for controlling the switching.
A signal input to the transmitting part is distributed by the one-to-one line switching equipment and transferred to a hot line or a standby line, and the transferred signal is received by the one-to-one line switching equipment at the receiving part.
In such a system, it is sometimes necessary to change over a unit in the one-to-one line switching equipment even during use.
2. Description of the Related Art
Conventionally, the distribution of the input signal at the transmitting part is carried out by using a relay contact or a hybrid circuit in the one-to-one line switching equipment, and at the receiving part, the signal transferred from the transmitting part is received through a relay contact in the one-to-one line switching equipment at the receiving part by selectively switching the relay contact to the hot line side or to the standby line side. The unit, such as the hybrid circuit or the relay contact, is formed on a printed circuit board (PCB) which is removably attached to a mother board on which the corresponding transmitting part or receiving part is formed. The removal of the PCB is often necessary when a fault occurs in the transmitting part or in the receiving part, and the faulty PCB or the relay contact must be replaced by a new board or contact.
Since, however, the hybrid circuit or the relay contact is connected to both the hot line and the standby line, the hybrid circuit or the relay contact cannot be actually removed from the mother board when the system is in use.
Therefore, in the conventional system, the removal and the change over of the hybrid circuit or the relay contact must be carried out while the system is not in use, and this is usually at a very inconvenient time, and thus the maintenance becomes cumbersome and expensive.